1. Field of Invention
Embodiments of the invention relate generally, but are not limited to, methods and apparatus for pumping blood.
2. Discussion of Related Art
In the treatment of a number of medical conditions, it is often desirable or necessary to aid blood flow in a patient. For example, during the performance of certain surgical procedures involving the heart, external devices may be needed to aid in the circulation of blood through the body. In other situations, the body may be incapable of sufficiently providing blood flow due to a failing, traumatized or infarcted heart.
Numerous devices have been developed that may replace portions of the heart and/or provide temporary or permanent assistance to the heart and increase the flow of blood through the body. These devices include cardiac assist pumping balloons that may be inserted into any large artery, such as the femoral artery, as part of a standard catheterization procedure. Cardiac assist pumping balloons are particularly advantageous in that implementation of these devices does not typically require major thoracic or otherwise invasive surgery. Catheter based balloon pumps have been primarily used to provide minimal cardiac support by reducing afterload to the heart.
Other balloon pumps have been used to pump blood from the heart. However, typically these devices have required the use of numerous input and output valves. One example of a balloon pump using an input valve is provided in U.S. Pat. No. 5,928,132 to Leschinsky, which is incorporated by reference herein. The use of input valves in balloon pumps can increase the cost and reliability of the pumps and may provide undesirable resistance to blood flow. One drawback with typical blood pumps designed for percutaneous insertion is that size limitations dictated by the insertion method limit the flow rate of blood from these devices, and pressure drops associated with input valves can become significant in small diameter tubes used in percutaneous blood pumps.